Breathable, hydrophobic and low-reflection electromagnetic shielding fabric and preparation method thereof

Abstract

The invention discloses a breathable, hydrophobic and low-reflection electromagnetic shielding fabric and a preparation method thereof, and the preparation method comprises the following steps: coating a coupling agent modified cotton fabric substrate with a magnetic carbon nanomaterial, then taking the coupling agent modified cotton fabric substrate as a receiving electrode, and taking a double-sided electrostatic spinning hydrophobic polyurethane microfiber film as an isolation protection layer. The magnetic carbon nanomaterial has good impedance matching and abundant loss mechanism, so that the fabric shows efficient electromagnetic shielding performance mainly based on absorption. Due to good conductivity, the shielding coating can be used as a receiving electrode for electrostatic spinning, electrostatic force attracts a spinning solution into gaps of the fabric, so that the isolating layer is tightly coated on the fabric, the use fastness of the shielding coating is further improved, and the shielding coating has a hydrophobic function. In addition, the electromagnetic shielding fabric also has excellent air permeability and comfortable hand feeling.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding materials, and in particular to a breathable, hydrophobic and low-reflective electromagnetic shielding fabric and a preparation method thereof. Background Art

[0002] Electromagnetic wave pollution caused by electronic devices and wireless communications can interfere with other electronic devices and pose potential health risks to humans who are exposed to it for a long time. Therefore, the development of wearable electromagnetic shielding materials is crucial to protecting human health. The manufacture of electromagnetic shielding materials on rubber elastomers and plastic films always leads to limited breathability and increased risk of inflammation. The network structure and porosity of the fabric give it excellent air permeability and moisture permeability, controllable heat transfer, uniform stress distribution, increased deformability and good flexibility. Traditional metal wire woven fabrics and metal-plated fabrics exhibit excellent electromagnetic wave reflection performance due to their significant conductivity, but their absorption capacity is weak due to impedance mismatch, which easily causes secondary electromagnetic pollution. In addition, their easy corrosion, poor flexibility and high density disadvantages hinder wearing comfort.

[0003] Therefore, the prior art has defects and needs to be improved. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a breathable, hydrophobic and low-reflective electromagnetic shielding fabric and a preparation method thereof; the magnetic carbon nanomaterial has good impedance matching and rich electromagnetic loss mechanisms, so that the fabric exhibits high-efficiency electromagnetic shielding performance mainly based on absorption; the electrospun isolation layer is tightly embedded in the gaps between the yarns, serving as a hydrophobic and isolation layer, thereby improving the durability of the electromagnetic shielding coating without losing wearing performance.

[0005] The technical solutions of the present invention are as follows: A method for preparing breathable, hydrophobic and low-reflective electromagnetic shielding fabric comprises coating a magnetic carbon nanomaterial on a coupling agent-modified cotton fabric substrate, which is then used as a receiving electrode, and a double-sided electrostatically spun hydrophobic polyurethane microfiber film is used as an isolation and protective layer.

[0006] The preparation method comprises the following steps: Step (1): adding oxidized carbon nanotubes to a solvent, and then adding Fe(NO3)3 and M(NO3)2, where M is a transition metal ion; the mixture is ultrasonically dispersed, the solvent is removed, and then calcined under an inert atmosphere to modify the spinel ferrite on the carbon nanomaterial to obtain a magnetic carbon nanomaterial loaded with spinel ferrite; Step (2): adding the magnetic carbon nanomaterial and the surfactant into deionized water, stirring and ultrasonically dispersing the water to obtain a magnetic carbon nanomaterial dispersion; Step (3): placing the pre-cleaned cotton fabric substrate in a coupling agent solution for immersion, taking it out, washing, and drying it to obtain a coupling agent-modified cotton fabric; Step (4): immersing the coupling agent-modified base fabric described in step (3) into the magnetic carbon nanomaterial dispersion described in step (2), taking it out and drying it in an oven, and then soaking it in deionized water to remove the surfactant and the unfixed magnetic carbon nanomaterial, repeating this process several times to adjust the loading mass fraction of the magnetic carbon nanomaterial on the fabric, and obtaining a magnetic carbon nanomaterial-coated fabric after drying; Step (5): Fix the magnetic carbon nanomaterial coated fabric described in step (4) on the receiving roller of the electrospinning device, connect the electrodes, and electrospin a microfiber film on one side as a protective layer and an isolation layer; then repeat this process on the other side to obtain a magnetic carbon nanomaterial coated fabric with an electrospun microfiber film.

[0007] In the preparation method, the transition metal element in step (1) is one or more of manganese, iron, cobalt, nickel, copper or zinc.

[0008] In the preparation method, the mass ratio of the carbon nanomaterial to the spinel nanoparticles in step (1) is 1:0.5 to 1:3.

[0009] In the preparation method, the concentrations of the surfactant and the magnetic carbon nanomaterial in deionized water in step (2) are both 0.1-1.0 wt.%.

[0010] In the preparation method, the base fabric in step (3) is a woven fabric, knitted fabric or non-woven fabric mainly composed of cotton fibers, and the fabric weight is 60-300 g / m 2 .

[0011] In the preparation method, the coupling agent in step (3) includes but is not limited to dopamine hydrochloride, titanate coupling agent, silane coupling agent and aluminate compound.

[0012] In the preparation method, the coating loading of the magnetic carbon nanomaterial coated fabric in step (4) is 0.1%~2.0 wt.%, and the sheet resistance is 10~100 Ω / sq.

[0013] The preparation method, the preparation method of the electrospun microfiber layer in step (5) is as follows: 1-5 wt.% polystyrene particles and 5-15 wt.% thermoplastic polyurethane particles are added to an N, N-dimethylformamide / tetrahydrofuran mixed solvent (mass ratio 1:1), and stirred to completely dissolve them; then, the cotton / magnetic carbon nanomaterial composite fabric with conductive copper foil attached to both ends is fixed on a receiving roller, the applied voltage and feed rate are set to 10-30 kV and 0.05~0.3 mL / h, the distance from the spinneret tip is 5-20 cm, and after spinning for 30~120 min, it is transferred to a 40~80℃ oven and placed for 1~3 h to completely remove the solvent; then the same spinning process is performed on the other side.

[0014] A magnetic carbon nanomaterial coated fabric with an electrospun microfiber layer prepared according to any of the preparation methods.

[0015] Compared with the existing technology, the present invention has the following advantages: magnetic carbon nanomaterials can provide high-efficiency electromagnetic shielding based on absorption, and the electromagnetic wave shielding and absorption mechanisms include interface reflection, multiple reflection, conduction loss, magnetic loss and polarization loss; the conductivity of magnetic carbon nanomaterials enables the composite fabric to be used as a receiving electrode for electrospinning, and the electrostatic force attracts the ejected spinning solution into the gaps in the fabric, and after fiberization, it is tightly adhered to the fabric, thereby improving the durability of the electromagnetic shielding coating and having a hydrophobic function; the shielding layer and the isolation layer do not seriously damage the original air permeability and flexibility of the fabric substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the steps of the preparation method of the present invention; Figure 2 are optical images of (a) plain cotton fabric and (b) CNT@CoFe2O4 coated composite fabric provided in Example 2; (c) and (d) are SEM images of the CNT@CoFe2O4 coated composite fabric at different magnifications; Figure 3 are optical and SEM images of the plain cotton / CNT@CoFe2O4 / electrospun microfiber film layer composite fabric provided in Example 3; Figure 4 is a water contact angle image of the cotton / magnetic graphene / electrospun microfiber layer composite fabric provided in Example 4; Figure 5 : (a) electromagnetic interference shielding (EMI SE) curves of the cotton / CNT / electrospun microfiber layer composite fabric provided in Example 1 and the cotton / CNT@CoFe2O4 / electrospun microfiber layer composite fabric provided in Example 3; (b) reflection shielding (SE R ) and Absorption Shielding (SE A ) to the total shield (SET ) performance contribution; Figure 6 is an optical image of the plain cotton / electrospun microfiber layer composite fabric provided in Comparative Example 3; DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to specific embodiments.

[0018] Example 1: Preparation of magnetic carbon nanotubes CNT@CoFe2O4: Pure carbon nanotubes were sonicated in a concentrated sulfuric acid / nitric acid mixture (3:1) for 2 hours to slightly oxidize the surface. 100 mg of oxidized carbon nanotubes were added to 20 mL of ethanol, followed by 344 mg of Fe(NO₃)₃·9H₂O and 124 mg of Co(NO₃)₂·6H₂O. After ultrasonic dispersion, the mixture was transferred to a 120°C oven and heated until it became a paste, then maintained at 100°C for 8 hours. The resulting powder was then transferred to a tube furnace and calcined at 550°C in Ar for 2 hours, modifying the carbon nanomaterial with spinel ferrite to yield carbon nanotubes loaded with magnetic cobalt ferrite nanoparticles (CNT@CoFe₂O₄).

[0019] Example 2: Preparation of CNT@CoFe2O4 coated cotton composite fabric: The density after cleaning is 180 g / m 2 Plain cotton fabric was immersed in a dopamine hydrochloride solution at a concentration of 8 mmol / mL and a pH of 8.5 for 6 hours, then washed and dried. A CNT@CoFe2O4 dispersion was then prepared by adding 1.0 g of CNT@CoFe2O4 and 1.0 g of sodium dodecylbenzenesulfonate to 100 mL of deionized water and ultrasonically dispersing the mixture for 60 minutes.

[0020] The treated cotton fabric was immersed in the dispersion for 5 minutes and then dried in an oven at 140°C. This process was repeated to adjust the coating weight to 2.0 wt.%. The fabric was then washed with deionized water to remove the surfactant and unattached CNT@CoFe2O4. After drying, the CNT@CoFe2O4-coated cotton composite fabric was obtained.

[0021] like Figure 2(a) and (b) are optical images of the original plain-weave cotton fabric and the CNT@CoFe2O4-coated cotton composite fabric, respectively. The fabric changes from its original white color to the black color of the CNT@CoFe2O. (c) is a SEM image of the CNT@CoFe2O4-coated cotton composite fabric, showing the rough surface after the deposition of CNT@CoFe2O4. A further magnified image (d) reveals the uniform CNT@CoFe2O4 network structure.

[0022] Example 3: Preparation of cotton / CNT@CoFe2O4 / electrospun microfiber film composite fabric: 5 wt.% polystyrene particles and 10 wt.% thermoplastic polyurethane particles were added to a 1:1 DMF / THF mixture and magnetically stirred to obtain a completely dissolved spinning solution. A cotton / CNT@CoFe2O4 composite fabric, with conductive copper foil attached to each end, was then mounted on a receiving roller at 100 rpm, 10 cm from the spinneret tip. The voltage between the receiving electrode and the spinneret electrode was set to 15 kV, and the feed rate was set to 0.1 mL / h. After spinning for one hour, the fabric was removed and placed in a 60°C oven for two hours to completely remove the solvent. This process was then repeated for the other side.

[0023] like Figure 3 (a) and (b) show optical and SEM images of the cotton / CNT@CoFe2O4 / electrospun microfiber layer composite fabric, respectively. It can be seen that the electrospun microfiber layer is tightly attached to the cotton / CNT@CoFe2O4 fabric, allowing the fabric's topology to be discerned. This is because the conductive cotton / CNT@CoFe2O4, after being connected to the electrodes, provides a high Coulomb attraction, allowing the oppositely charged spinning solution to enter the gaps in the base fabric. This also allows the charge in the spinning solution to be quickly neutralized and dissipated, without affecting subsequent spinning solution accumulation.

[0024] Example 4: Preparation of cotton / magnetic graphene / electrospun microfiber layer composite fabric: 1.0 g of graphene@NiFe2O4 (NiFe2O4 content: 60 wt.%) and 1.0 g of sodium dodecylbenzenesulfonate were added to 100 mL of deionized water and ultrasonically dispersed for 60 minutes. The dispersion was applied to a spray gun and sprayed onto the fabric. After drying and rinsing, the surfactant was removed. The spray coating time was adjusted to a deposition mass of approximately 2.5 wt.% of graphene@NiFe2O4. The fabric was then secured to the receiving roller of the electrospinning machine using conductive tape, 10 cm from the spinneret tip. The voltage between the receiving electrode and the nozzle electrode was set to 15 kV, and the feed rate was set to 0.1 mL / h. After spinning for one hour, the fabric was removed and placed in a 60°C oven for two hours to completely remove the solvent. This process was repeated for the other side.

[0025] like Figure 4 As shown, water droplets form on the surface of the cotton / magnetic graphene / electrospun microfiber composite fabric, with a water contact angle of approximately 137°. Furthermore, after tilting, the water droplets exhibit good fluidity, leaving no water marks.

[0026] Comparative Example 1: Preparation of cotton / carbon nanotube / electrospun microfiber film composite fabric: First, a 1.0 wt.% pure carbon nanotube aqueous dispersion was prepared, and a density of 180 g / m 2 Plain cotton fabric was immersed in the dispersion and dried in an oven at 140°C. This process was repeated to adjust the coating weight to 1.0 wt.%. The fabric was then washed with deionized water to remove the surfactant and unattached carbon nanotubes, and dried to obtain a cotton / carbon nanotube composite fabric.

[0027] 5 wt.% polystyrene particles and 10 wt.% thermoplastic polyurethane particles were added to a 1:1 DMF / THF mixture and magnetically stirred to obtain a completely dissolved spinning solution. The cotton / CNT composite fabric, with conductive copper foil attached to each end, was then mounted on a receiving roller rotating at 100 rpm, 10 cm from the spinneret tip. The voltage between the receiving electrode and the spinneret electrode was set to 15 kV, and the feed rate was set to 0.1 mL / h. After spinning for one hour, the fabric was removed and placed in a 60°C oven for two hours to completely remove the solvent. This process was then repeated for the other side.

[0028] The electromagnetic parameters of the composite fabrics provided in Comparative Example 1 and Example 3 in the range of 8.2-12.4 GHz were measured using an appropriate network analyzer, and their shielding effectiveness against electromagnetic waves was calculated. Figure 5 (a) is the electromagnetic interference shielding efficiency (EMI SE) curve, Figure 5 (b) is reflective shielding (SE R ) and Absorption Shielding (SE A ) to the total shield (SE T ) performance contribution value. It can be seen that the composite fabric provided in Example 3 has better EMI SE. More importantly, the SE of the composite fabric provided in Example 3 R Compared with the composite fabric provided in Comparative Example 1, it is lower, which means that the composite fabric provided in Example 3 has weaker reflected electromagnetic wave pollution while providing more efficient EMI SE.

[0029] Comparative Example 2: Preparation of cotton / CNT@CoFe2O4 / waterborne acrylic resin coating composite fabric: First, prepare the aqueous dispersion of CNT@CoFe2O4 by adding 0.5 g of CNT@CoFe2O4 and 0.5 g of sodium dodecylbenzenesulfonate into 100 mL of deionized water and ultrasonically disperse for 60 minutes. 2 A plain cotton fabric was immersed in this dispersion and dried in a 140°C oven. The fabric was then washed with deionized water to remove the surfactant and unattached CNT@CoFe2O4. After drying, a cotton / CNT@CoFe2O4 composite fabric was obtained. This process was repeated to adjust the coating weight to 2.0 wt.%. Finally, the cotton / CNT@CoFe2O4 composite fabric was immersed in a 30 wt.% aqueous polyurethane solution for 10 minutes and dried in a 40°C oven to cure. The resulting cotton / CNT@CoFe2O4 / waterborne acrylic resin coating composite fabric had a harder feel and almost no breathability compared to Example 3.

[0030] Comparative Example 3: Preparation of cotton / electrospun microfiber layer: The cotton fabric was fixed on the receiving roller of electrospinning with conductive tape, 10 cm away from the tip of the spinneret. The voltage between the receiving electrode and the nozzle electrode was set to 15 kV, and the feed rate was set to 0.1 mL / h. After spinning for 1 hour, the fabric was removed and transferred to a 60°C oven for 2 hours to completely remove the solvent.

[0031] like Figure 6 As shown, compared with Example 3, when the original cotton fabric was fixed to the receiving electrode surface, the electrospun microfiber film failed to adhere to the fabric substrate and could be easily separated. This is because the non-conductive original cotton fabric only intercepted the spinning solution on the surface and could not be embedded in the fabric. The accumulated charge could not be effectively released, hindering the subsequent close accumulation of the same-charged spinning solution.

[0032] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a breathable, hydrophobic and low-reflective electromagnetic shielding fabric, characterized in that: The magnetic carbon nanomaterial is coated onto a coupling agent-modified cotton fabric substrate, which is then used as a receiving electrode, and a double-sided electrospun hydrophobic polyurethane microfiber film is used as an isolation and protective layer.

2. The preparation method according to claim 1, characterized in that The following steps are involved: Step (1): adding oxidized carbon nanotubes to a solvent, and then adding Fe(NO3)3 and M(NO3)2, where M is a transition metal ion; the mixture is ultrasonically dispersed, the solvent is removed, and then calcined under an inert atmosphere to modify the spinel ferrite on the carbon nanomaterial to obtain a magnetic carbon nanomaterial loaded with spinel ferrite; Step (2): adding the magnetic carbon nanomaterial and the surfactant into deionized water, stirring and ultrasonically dispersing the water to obtain a magnetic carbon nanomaterial dispersion; Step (3): placing the pre-cleaned cotton fabric substrate in a coupling agent solution for immersion, taking it out, washing, and drying it to obtain a coupling agent-modified cotton fabric; Step (4): immersing the coupling agent-modified base fabric described in step (3) into the magnetic carbon nanomaterial dispersion described in step (2), taking it out and drying it in an oven, and then soaking it in deionized water to remove the surfactant and the unfixed magnetic carbon nanomaterial, repeating this process several times to adjust the loading mass fraction of the magnetic carbon nanomaterial on the fabric, and obtaining a magnetic carbon nanomaterial-coated fabric after drying; Step (5): Fix the magnetic carbon nanomaterial coated fabric described in step (4) on the receiving roller of the electrospinning device, connect the electrodes, and electrospin a microfiber film on one side as a protective layer and an isolation layer; then repeat this process on the other side to obtain a magnetic carbon nanomaterial coated fabric with an electrospun microfiber film.

3. The preparation method according to claim 2, characterized in that The transition metal element in step (1) is one or more of manganese, iron, cobalt, nickel, copper or zinc.

4. The preparation method according to claim 2, characterized in that The mass ratio of the carbon nanomaterial to the spinel nanoparticles in step (1) is 1:0.5 to 1:

3.

5. The preparation method according to claim 2, characterized in that The concentrations of the surfactant and the magnetic carbon nanomaterial in deionized water in step (2) are both 0.1-1.0 wt.%.

6. The preparation method according to claim 2, characterized in that The base fabric in step (3) is a woven fabric, knitted fabric or non-woven fabric mainly made of cotton fiber, and the fabric weight is 60~300 g / m 2 .

7. The preparation method according to claim 2, characterized in that The coupling agent described in step (3) includes but is not limited to dopamine hydrochloride, titanate coupling agent, silane coupling agent and aluminate compound.

8. The preparation method according to claim 2, characterized in that The coating loading of the magnetic carbon nanomaterial coated fabric in step (4) is 0.1%~2.0 wt.%, and the square resistance is 10~100 Ω / sq.

9. The preparation method according to claim 2, characterized in that The preparation method of the electrospun microfiber layer described in step (5) is as follows: 1-5 wt.% polystyrene particles and 5-15 wt.% thermoplastic polyurethane particles are added to an N, N-dimethylformamide / tetrahydrofuran mixed solvent (mass ratio 1:1) and stirred to completely dissolve them; then, the cotton / magnetic carbon nanomaterial composite fabric with conductive copper foil attached to both ends is fixed on a receiving roller, the applied voltage and feed rate are set to 10-30 kV and 0.05~0.3 mL / h, the distance from the spinneret tip is 5-20 cm, and after spinning for 30~120 min, it is transferred to a 40~80℃ oven and placed for 1~3 h to completely remove the solvent; then the same spinning process is performed on the other side.

10. A magnetic carbon nanomaterial coated fabric with an electrospun microfiber layer prepared according to the preparation method of any one of claims 1 to 9.

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